Dual CAN Master Redundancy in PLC-Based Subsea Control
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Solution Overview
Problem
In PLC-based control systems for drilling rigs, particularly in subsea environments, the lack of availability of certain CAN-open protocol features, such as the flying master functionality, limits redundancy and flexibility, leading to potential system failures and operational disruptions when primary components fail.
Innovation Solution
Implementing a dual CAN master configuration with redundant PLC and CAN modules, where one module acts as a backup to the other, enabling seamless fail-over and maintaining system operation even if primary components fail, through software logic and ProfiNet or CAN-open device expansion modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single CAN master module is used in the PLC-based control system, then the device complexity is reduced, but the system reliability deteriorates due to lack of redundancy
Solution Approach 1:
The system pre-configures a secondary CAN master module in standby mode before any failure occurs. This preliminary preparation ensures that redundancy is already in place, allowing immediate failover to the secondary module if the primary module fails, thus improving reliability without adding operational complexity.
Solution Approach 2:
The system implements a hot-swappable redundancy architecture where the secondary CAN master module can take over immediately upon primary module failure. The failed module can then be replaced or recovered, ensuring continuous system operation and improved reliability while maintaining manageable device complexity through automated switching.
2Adaptability or versatility
If CAN-open protocol features like flying master are not available, then the device complexity is reduced, but the system adaptability deteriorates in terms of redundancy and flexibility
Solution Approach 1:
The system pre-establishes the capability for multiple CAN master modules through hardware configuration and software logic, even though the standard CAN-open protocol doesn't support flying master. This preliminary setup enables the system to adapt to failures and reconfigure dynamically, improving flexibility without requiring complex protocol modifications.
Solution Approach 2:
The system implements dynamic role assignment where CAN modules can switch between primary and secondary roles based on operational status. This dynamic adaptability allows the system to respond to failures and reconfigure the CAN master configuration in real-time, enhancing system flexibility without adding permanent complexity to the device architecture.
Data Source
AI summary
A system for controlling equipment at a wellsite includes a surface PLC, a first subsea PLC, a second subsea PLC, a first CAN module, a second CAN module, and a CAN network. The surface PLC is configured to receive a parameter that is measured by a sensor and to transmit a first signal to the first subsea PLC, the second subsea PLC, or both in response to the parameter. The first subsea PLC or the second subsea PLC, or both are configured to transmit a second signal to the first CAN module, the second CAN module, or both in response to the first signal. The first CAN module, the second CAN module, or both are configured to transmit a third signal to the CAN network in response to the second signal. The CAN network is configured to control the equipment in response to the third signal.